在高放废物处置库中,放射性核素由于地下水的侵入而随地下水一同迁移,在多孔介质中由于放射性核素在渗流中的速度不同,必然会产生弥散现象。作为高毒性核素,~(99)Tc在花岗岩中的弥散程度是我国北山预选场址安全性评价的重要依据,因此本文采用脉冲源法测定了不同温度和不同压力下~(99)Tc在花岗岩中的弥散系数,计算了花岗岩的弥散度。1锝在花岗岩中的弥散实验制备好的花岗岩柱体(直径为2.5 cm,长为4.5~5.0 cm)置于不锈钢夹持器中,外围用橡胶 In HLW reservoirs, radionuclides migrate with groundwater due to the intrusion of groundwater. In porous media, due to the different velocities of radionuclides in percolation, diffusion phenomena inevitably occur. As a highly toxic nuclide, the diffusion of ~ (99) Tc in granite is an important basis for the safety assessment of pre-selected sites in Beishan of China. Therefore, the pulse source method was used to determine the emission of ~ (99) Tc at different temperatures and pressures The dispersion coefficient of granite, calculate the dispersion of granite. Dispersion experiment of technetium in granite Granite columns (2.5 cm in diameter and 4.5-5.0 cm in length) were prepared in a stainless steel holder with rubber